ABSTRACT Transient global cerebral ischemia results in selective neuronal death in the vulnerable hippocampal CA1 pyramidal neurons in a delayed manner. Hyperglycemia accelerates and exacerbates neuronal damage in this region. The object of this study was to determine whether hyperglycemia-enhanced damage is associated with increased production of superoxide anion after ischemia. The results showed that hyperglycemic ischemia caused a significant increase of superoxide production in the hippocampal CA1 neurons compared to normoglycemic animals after 18 h of recirculation, suggesting that enhanced superoxide anion production may mediate the hyperglycemia-accelerated and -enhanced neuronal death in the hippocampal CA1 area after ischemia and reperfusion.

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The long-term impacts of cerebral ischemia and diabetic ischemia on astrocytes and oligodendrocytes have not been defined. The objective of this study is to define profile of astrocyte and changes of myelin in diabetic and non-diabetic rats subjected to focal ischemia.Focal cerebral ischemia of 30-min duration was induced in streptozotocin-induced diabetic and vehicle-injected normoglycemic rats. The brains were harvested for immunohistochemistry of glial fibrillary acidic protein (GFAP) and 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) at various reperfusion endpoints ranging from 30 min up to 28 days. The results showed that activate astrocytes were observed after 30 min and peaked at 3 h to 1 day after reperfusion in ischemic penumbra, and peaked at 7 days of reperfusion in ischemic core. Diabetes inhibited the activation of astrocytes in ischemic hemisphere. Demyelination occurred after 30 min of reperfusion in ischemic core and peaked at 1 day. Diabetes caused more severe demyelination compared with non-diabetic rats. Remyelination started at 7 days and completed at 14 and 28 days in ischemic region. Diabetes inhibited the remyelination processes. It is concluded that ischemia activates astrocytes and induces demyelination. Diabetes inhibits the activation of astrocytes, exacerbates the demyelination and delays the remyelination processes. These may contribute to the detrimental effects of hyperglycemia on ischemic brain damage.

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Diabetes mellitus and impaired glucose metabolism are the most important risk factors for stroke. We recently demonstrated that cerebral ischemic stress causes hyperglycemia (i.e., post-ischemic hyperglycemia) and may worsen ischemic neuronal damage in a mouse model of focal ischemia. However, the detailed mechanisms are still unknown. The sodium-glucose transporter (SGLT) generates inward currents in the process of transporting glucose into cells, resulting in depolarization and increased excitability, which is well known to be caused by cerebral ischemia. Hence, we focused on the role of SGLT on the development of neuronal damage using a global ischemic model. Male ddY mice were subjected to 30min of bilateral carotid artery occlusion (BCAO). The neuronal damage was estimated by histological analysis using HE staining on day 3 after BCAO. Intraperitoneal (i.p.) administration of phlorizin (a specific and competitive inhibitor of SGLT, 200mg/kg immediately after reperfusion) suppressed the development of post-ischemic hyperglycemia on day 1 after BCAO. In contrast, intracerebroventricular (i.c.v.) administration of phlorizin (40μg/mouse immediately and 6h after reperfusion) had no effect on day 1 after BCAO. Interestingly, the development of ischemic neuronal damage was significantly suppressed by i.p. and i.c.v. administration of phlorizin on day 3 after BCAO. In addition, BCAO-induced spasticity was significantly suppressed by PHZ (40μg/mouse, i.c.v.) from using gait analysis. Our results indicated that cerebral SGLT was involved in the development of ischemic neuronal damage in global ischemia.

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Aims:Chronicethanolconsumptionleadstooxidativedamageinthecentralnervoussysteminducingneuronaldegeneration and impairment of brain functions. Nevertheless, it has been reported that grape polyphenols might prevent the alluded ethanol effects. We have reported that prolonged red wine intake improves hippocampal formation oxidative status, a finding not replicated using Port wine. Thus, we thought of interest to compare the effects of chronic ingestion of these wines in the morphology of dentate gyrus (DG) neurons that are particularly vulnerable to alcohol effects. Methods: Six-month-old Wistar rats were fed either with red wine or Port wine (both with 20% ethanol content, v/v), and the results were compared with 20% (v/v) ethanol-treated, ethanol/glucose and pair-fed control groups. After 6 months of treatment, the layer volumes of the DG and the total number of granule and hilar neurons were estimated. The dendritic trees of granule cells were also studied in Golgi-impregnated material. Results: The number of granule cells and the DG layer volumes were similar among all groups. However, the number of hilar neurons was reduced in Port wine, ethanol-treated and ethanol/glucose animals. Furthermore, the granule cells from these groups showed a decrease in the total dendritic length. Conclusions: Although the Port wine and red wine have similar amounts of flavanols with identical ability to protect against oxidative stress, the differences observed are probably related to the very dissimilar processes of wine production, leading in Port wine to a high content of sugars, which are known to have potent pro-oxidant effects.

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